Calcium electrode studies: These studies involve the application of ion-exchange calcium electrodes to clinical, physiologic and physico- chemical problems in calcium metabolism. Specific projects include studies of protein-binding by serum proteins in normal and pathologic states, pH and temperature nomograms for serum ionized calcium (Ca ions), and kinetic models for salivary and pancreatic secretion. Ammonia electrode studies: These studies involve the application of a recently-developed ammonia electrode to biologic systems. Specific projects include ammonia in urine, sweat and saliva, and the physico- chemical state of ammonia in human serum and whole blood. Small intestinal absorption-secretion studies: The objective of these studies (dog and rabbit) is to define the role of ion-exchange mechanisms in cation and anion transport, the effects of hormones, and the state of hydration of the animal.